Partial support is requested for a Workshop on Site-specific Recombination and Transposition to be held on September 12-16, 1990, at the Marine Biological Laboratory in Woods Hole, Massachusetts. The purpose of this workshop is to assemble for discussions a select but representative group of scientists who are actively working at the forefront of research on the biochemical mechanisms for site-specific recombination and transposition. This interrelated group of reactions lie at the heart of a number of very important biological processes: integration of retroviruses including those responsible for AIDS and certain forms of cancer, generation of antibody diversity, transmission of antibiotic resistance genes, rearrangement of bacterial chromosomes, and mobility of eukaryotic introns. The oral presentations at this Workshop will emphasize the mechanistic aspects of these recombination reactions. A specialized meeting for leaders in this field should be both timely and productive. There has been rapid recent progress in many different systems. Furthermore, it is becoming increasingly apparent that reactions occurring in eukaryotic organisms are intimately related to those identified in bacteria: integration of AIDS virus and other retroviruses is mechanistically closely related to integration of bacterial transposons, site specific immunoglobulin rearrangements are closely related to prokaryotic site specific recombination reactions, etc. In promoting the exchange of insights and information from different systems, the Workshop should greatly enhance our basic understanding of all of these reactions. In addition, in the particular case of AIDS virus and other retroviruses, it should further the goal of using the recombination reaction as a target therapeutic intervention. The roster of speakers includes scientists who have applied biochemical, genetic and topological analysis including several who have pushed the analysis of recombination for the first time into the realm of enzyme kinetics. Topics will include retroviral integration, reactions of the integrase and resolvase families, Holliday junctions, immunoglobulin rearrangements, prokaryotic transposable elements, and Drosophila P elements. We are also encouraging poster presentations from scientists working in systems which are not yet amenable to mechanistic analysis. This should serve both to broaden the biological base of the meeting and to encourage those working in relatively undeveloped systems to undertake a more mechanistic approach. The meeting will be limited to 100-135 participants. This number is sufficient to include all of the principal investigators who are working productively in this area as well as a reasonable sampling of postdoctoral fellows and an occasional outstanding graduate student. However, this number is small enough that efficient interchange amongst all of the participants is still possible.